Six genetic diseases have been identified to date that involve alterations in purine metabolism. These include arthritis, Lesch- Nyhan disease, Severe Combined Immunodeficiency, and Myoadenylate disease. Understanding the nature and regulation of the purine biosynthetic pathway on a molecular basis will be important to the understanding and treatment of any pathological alterations of this pathway presently known or that may be identified in the future. This study proposes to isolate and characterize a full-length cDNA clone for glutamine PRPP amidotransferase, the first and rate-controlling enzyme of the purine biosynthetic pathway. The underlying premise of this proposed work is that while the structures of the enzymes of purine biosynthesis have evolutionary diverged their functions have not. We propose to isolate a functional full-length cDNA clone for human glutamine PRPP amidotransferase by screening cDNA gene banks in procaryotic expression vectors for their ability to complement the corresponding E. coli purine mutation purF). The cDNA clones isolated will be characterized by restriction enzyme mapping and a representative clone will be sequenced. The isolation of a full-length cDNA clone will be confirmed by comparison to the size of the mature mRNA determined by Northern blotting and by comparison of the size of the encoded protein to the characterized enzyme. A cDNA clone will then be used as a probe to isolate clones from genomic libraries containing the structural gene. The total size of the structural gene will be estimated by restriction enzyme mapping and Southern hybridization. The 5'-end of the cDNA clones will be used to identify the corresponding region of the structural gene. The sequence of the control region will be determined and the transcription initiation points will be determined by S1 nuclease mapping. The potential regulatory sequences will be identified by comparison to known regulatory sequences and the control regions of related genes.